/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/************************************************************************************
 * drivers/serial/serialirq.c
 *
 *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ************************************************************************************/

/************************************************************************************
 * Included Files
 ************************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <semaphore.h>
#include <debug.h>
#include <tinyara/serial/serial.h>

/************************************************************************************
 * Pre-processor Definitions
 ************************************************************************************/

/************************************************************************************
 * Private Types
 ************************************************************************************/

/************************************************************************************
 * Private Function Prototypes
 ************************************************************************************/

/************************************************************************************
 * Private Variables
 ************************************************************************************/

/************************************************************************************
 * Private Functions
 ************************************************************************************/

/************************************************************************************
 * Public Functions
 ************************************************************************************/

/************************************************************************************
 * Name: uart_xmitchars
 *
 * Description:
 *   This function is called from the UART interrupt handler when an interrupt
 *   is received indicating that there is more space in the transmit FIFO.  This
 *   function will send characters from the tail of the xmit buffer while the driver
 *   write() logic adds data to the head of the xmit buffer.
 *
 ************************************************************************************/

void uart_xmitchars(FAR uart_dev_t *dev)
{
	uint16_t nbytes = 0;

	/* Send while we still have data in the TX buffer & room in the fifo */

	while (dev->xmit.head != dev->xmit.tail && uart_txready(dev)) {
		/* Send the next byte */

		uart_send(dev, dev->xmit.buffer[dev->xmit.tail]);
		nbytes++;

		/* Increment the tail index */

		if (++(dev->xmit.tail) >= dev->xmit.size) {
			dev->xmit.tail = 0;
		}
	}

	/* When all of the characters have been sent from the buffer disable the TX
	 * interrupt.
	 *
	 * Potential bug?  If nbytes == 0 && (dev->xmit.head == dev->xmit.tail) &&
	 * dev->xmitwaiting == true, then disabling the TX interrupt will leave
	 * the uart_write() logic waiting to TX to complete with no TX interrupts.
	 * Can that happen?
	 */

	if (dev->xmit.head == dev->xmit.tail) {
		uart_disabletxint(dev);
	}

	/* If any bytes were removed from the buffer, inform any waiters there there is
	 * space available.
	 */

	if (nbytes) {
		uart_datasent(dev);
	}
}

/************************************************************************************
 * Name: uart_receivechars
 *
 * Description:
 *   This function is called from the UART interrupt handler when an interrupt
 *   is received indicating that are bytes available in the receive fifo.  This
 *   function will add chars to head of receive buffer.  Driver read() logic will
 *   take characters from the tail of the buffer.
 *
 ************************************************************************************/

void uart_recvchars(FAR uart_dev_t *dev)
{
	FAR struct uart_buffer_s *rxbuf = &dev->recv;
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
	unsigned int watermark;
#endif
	unsigned int status;
	int nexthead = rxbuf->head + 1;
	uint16_t nbytes = 0;

	if (nexthead >= rxbuf->size) {
		nexthead = 0;
	}
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
	/* Pre-calcuate the watermark level that we will need to test against. */

	watermark = (CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK * rxbuf->size) / 100;
#endif

	/* Loop putting characters into the receive buffer until there are no further
	 * characters to available.
	 */

	while (uart_rxavailable(dev)) {
		bool is_full = (nexthead == rxbuf->tail);
		char ch;

#ifdef CONFIG_SERIAL_IFLOWCONTROL
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
		unsigned int nbuffered;

		/* How many bytes are buffered */

		if (rxbuf->head >= rxbuf->tail) {
			nbuffered = rxbuf->head - rxbuf->tail;
		} else {
			nbuffered = rxbuf->size - rxbuf->tail + rxbuf->head;
		}

		/* Is the level now above the watermark level that we need to report? */

		if (nbuffered >= watermark) {
			/* Let the lower level driver know that the watermark level has been
			 * crossed.  It will probably activate RX flow control.
			 */

			if (uart_rxflowcontrol(dev, nbuffered, true)) {
				/* Low-level driver activated RX flow control, exit loop now. */

				break;
			}
		}
#else
		/* Check if RX buffer is full and allow serial low-level driver to pause
		 * processing. This allows proper utilization of hardware flow control.
		 */

		if (is_full) {
			if (uart_rxflowcontrol(dev, rxbuf->size, true)) {
				/* Low-level driver activated RX flow control, exit loop now. */

				break;
			}
		}
#endif
#endif

		ch = uart_receive(dev, &status);

		/* If the RX buffer becomes full, then the serial data is discarded.  This is
		 * necessary because on most serial hardware, you must read the data in order
		 * to clear the RX interrupt. An option on some hardware might be to simply
		 * disable RX interrupts until the RX buffer becomes non-FULL.  However, that
		 * would probably just cause the overrun to occur in hardware (unless it has
		 * some large internal buffering).
		 */

		if (!is_full) {
			/* Add the character to the buffer */

			rxbuf->buffer[rxbuf->head] = ch;
			nbytes++;

			/* Increment the head index */

			rxbuf->head = nexthead;
			if (++nexthead >= rxbuf->size) {
				nexthead = 0;
			}
		}
	}

	/* If any bytes were added to the buffer, inform any waiters there there is new
	 * incoming data available.
	 */

	if (nbytes) {
		uart_datareceived(dev);
	}
}
